[Analysis of restriction fragment length polymorphism (RFLP) of Mycobacterium tuberculosis strains isolated from patients with several episodes of tuberculosis].

Analysis of restriction fragment length polymorphism (RFLP), using a DNA probe directed against the insertion sequence IS6110, was applied to strains of Mycobacterium tuberculosis successively isolated from four patients. In order to determine the cause of recurrence in these patients, the RFLP patterns of the corresponding isolated were analyzed. The profils obtained from the strains isolated from each of the patients were identical, thus suggesting that a relapse, rather than an exogenous reinfection with a new strain, was the cause of recurrence. The RFLP patterns of successive isolated remained unchanged during periods of time ranging from 5 months to 7 years, and were not modified after development of rifampin resistance. These results demonstrate the stability of the polymorphism detected by the IS6110 probe. Therefore, RFLP analysis is a powerfull epidemiologic tool to distinguish relapse from exogenous reinfection.